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Design Manual Removal of Arsenic from Drinking Water Supplies by Iron Removal Process (78 pp, 1.8 MB) April 2006
This design manual presents the steps required to design and operate a water treatment plant for removal of arsenic (As) from drinking water supplies using iron removal processes. It also discusses the capital and operating costs, including the many variables that can raise or lower costs for identical treatment systems.
Iron removal processes are generally simple, reliable, and cost-effective. Arsenic removal is accomplished by adsorption of As(V) onto ferric hydroxides formed in the iron removal process. Several iron removal treatment methods can remove arsenic from drinking water supplies to levels below the new arsenic maximum contaminant level (MCL) of 0.010 mg/L; these methods include oxidation and filtration, and the use of solid oxidizing media products and manganese greensand. Many existing water utilities have much if not all of the appropriate technology in place for iron removal, but may need to modify or adjust the processes in order to meet the new MCL.
Iron removal processes have operational options that vary with the oxidants used and the media selected for filtration. Selection of the most appropriate process for a water supply should be evaluated on a life-cycle basis. This design manual provides examples for performing an economic evaluation, including the development of an equivalent annual cost. The arsenic removal capacity may be affected by the raw water quality, particularly hydrogen sulfide, organics, and, in some cases, the pH of the water. Treatment processes incorporating oxidants require careful handling and storage of corrosive chemicals, such as chlorine and potassium permanganate.